21-Sep-2018

Forensic Magazine feature: How human bias alters DNA software results

"It is a capital mistake to theorize before one has data. Insensibly one begins to twist facts to suit theories, instead of theories to suit facts." – Sherlock Holmes

What if DNA analysts could pick and choose their data? Or adjust software parameters to alter forensic match results? DNA evidence that excludes someone ("he's innocent") could then be twisted to include ("he's guilty").

In 2016, computer-analyzed evidence showed a defendant’s DNA was in a fingernail mixture. But the same software also showed he wasn’t in the mixture. A user could choose their data and parameters to get either match result.

In New York v. Hillary, "Different human choices of input data gave
diametrically opposed answers," writes Cybergenetics Dr. Mark Perlin
in his Forensic MagazineSuspect-centric bias in DNA mixture
interpretation feature article. "The software contradicted itself. It both included and excluded Hillary."